Anticorrosion lubricating compound

ABSTRACT

AN IMPROVED HEAVY DUTY COATING COMPOSITION FOR PROTECTION AGAINST CORROSION OF METALLIC SUBSTRATES AND FOR LUBRICATION OF METALLIC PARTS COMPRISES A SUBSTANTIALLY UNIFORM MIXTURE OF FROM ABOUT 40 TO ABOUT 70 WEIGHT PERCENT OF LEAD OXIDE IN PARTICULATE FORM HAVING AN AVERAGE PARTICLE DIAMETER SIZE OF FROM ABOUT 30-45 MICRONS AND AN ESSENTIALLY HOMOGENEOUS GREASE-CONTAINING VEHICLE. THE VEHICLE COMPRISES A MAJOR PROPORTION OF GREASE, PREFERABLY HEAVY DUTY GREASE, AND A MINOR PROPORTION OF LUBRICATING OIL, PREFERABLY HIGH PRESSURE LUBRICATING OIL. THE GREASE-CONTAINING VEHICLE IS NON-SEPARATING AND PREFERABLY THE GREASE IS PRESENT IN THE VEHICLE IN A WEIGHT RATIO TO THE OIL OF ABOUT 5:1. THE LEAD OXIDE PREFERABLY COMPRISES AT LEAST ONE OF PB3O4.

United States Patent Oice 3,642,625 ANTICORROSION LUBRICATING COMPOUND Stanley J. Caplan, Northridge, Califi, assiguor to Accralube Company, Northridge, Calif. No Drawing. Filed Oct. 1, 1969, Ser. No. 862,930 Int. Cl. C10m 5/02 U.S. Cl. 252-25 7 Claims ABSTRACT OF THE DISCLOSURE An improved heavy duty coating composition for protection against corrosion of metallic substrates and for lubrication of metallic parts comprises a substantially uniform mixture of from about 40 to about 70- weight percent of lead oxide in particulate form having an average particle diameter size of from about 30-45 microns and an essentially homogeneous grease-containing vehicle. The vehicle comprises a major proportion of grease, preferably heavy duty grease, and a minor proportion of. lubricating oil, preferably high pressure lubricating oil. The grease-containing vehicle is non-separating and preferably the grease is present in the vehicle in a weight ratio to the oil of about 5:1. The lead oxide preferably comprises at least one of PbO and Pb O BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to lubricating compounds, and more particularly to such compounds providing special anticorrosion protection.

(2) Description of the prior art Conventional heavy duty lubricants and protective coating compositions commonly employ organic constituents such as organic acids, organic amines, organic phosphates, polyhydric alcohols and sodium and calcium sulfonates as active protective ingredients. Certain lubricants contain oxidation inhibitors such as alkylphenols, thiophosphates and the like in concentrations of about 0.1 to about 1.0 percent by weight in a suitable vehicle. In certain instances lead-type soaps and various sulfur, chlorine and phosphorus-containing organic additives are used with or without fillers such as graphite, molybdenum disulfide, talc, asbestos and the like as additives in thickened lubricants for heavy duty use.

Such protective coatings for metallic substrates attempt to either isolate the substrate, as by a relatively impervious film, or to coat the substrate with an inhibitor that protects the metal by a controlled release of inhibitor ions or the like, or both. However, the described anticorrosive type lubricants and coating compositions generally are subject to certain problems. For example, most of such lubricants are expensive and have a limited temperature range of effective operation. When they break down under the stress of heat or friction they have a high residual ash content and may generate or release corrosive acids at a high conversion rate. Certain such lubricants and protective coating compositions exhibit low durability under extremely corrosive conditions such as salt water environ ments, high temperatures, high pressures and the like.

In order to overcome certain of the described deficiencies, attempts have been made in the past to add small amounts of metallic substances to the lubricants and coating compositions. When such compositions employ metallic oxides, such oxides are present only in very limited low concentrations normally of the order of about 0.5-2 percent by weight, and in no instance in a concentration of more than 10 weight percent. However, it has been found that the resulting compositions still are subject to 3,642,625 Patented Feb. 15, 1972 relatively rapid breakdown in salt water use, nor do they exhibit optimum characteristics when used as lubricants in heavy duty machinery containing bearings and other components having close tolerances. In view of the deficiencies of the known lubricant and grease-base protecting coating art, particularly with respect to use in heavy duty and highly corrosive environments it would be desirable to provide a simple, inexpensive durable coating and lubricating composition.

Accordingly it is a principal object of the present invention to provide an improved heavy duty coating composition for protection of metallic substrates, which composition also has lubricating properties.

It is a further object of the present invention to provide an improved coating and lubricating composition for use in corrosive environments, which composition has increased resistance to breakdown and wear.

It is also an object of the present invention to provide a simple, inexpensive heavy duty coating and lubricating composition for protection of metallic substrates which composition is not subject to the production of acids or the like corrosive substances and which does not depend upon the incorporation therein of expensive organic antioxidants.

Further objects and advantages of the present invention will be apparent from a study of the following de tailed description.

SUMMARY OF THE INVENTION In brief, the invention comprises a heavy duty coating composition for protection against corrosion of metallic substrates and for lubrication of metallic parts in the form of a substantially uniform mixture of from about 40 to about weight percent of lead oxide in particulate form having an average particle diameter size of from about 30-45 microns and an essentially homogeneous greasecontaining vehicle. The vehicle comprises a major proportion of grease, preferably heavy duty grease, and a minor proportion of lubricating oil, preferably high pressure lubricating oil. The grease-containing vehicle is nonseparating and preferably the grease is present in the vehicle in a weight ratio to the oil of about 5:1. The lead oxide preferably comprises at least one of PbO and Pb O The composition is capable of withstanding chemicals, salt water, acids, atmospheric corrosion, steam and high temperature and pressure While still providing suitable adhesion to metallic substrates and a lubricating effect at very low temperature. The composition is also effective as a rust inhibitor and serves as a protective coating against radiation, radio interference and corona.

LEAD OXIDES Now referring more particularly to said coating composition, said composition includes from about 40 to about 70 percent, by weight of said composition, of any suitable lead oxide in particulate form, for example, commercial or reagent grade particulate lead oxide. It is an important part of present invention to provide the lead oxide in a particle size range of from about 30 to about 45 microns. It has been discovered that when lead oxide particles of an average diameter size of about 5 to about 25 microns are employed in the composition in association with the essentially homogeneous grease-containing vehicle present in the composition, the lead oxide particles exhibit an acidic response during use of the composition and, acordingly, are unsuitable for long term anticorrosive protection, since acidic substances are themselves corrosive to metals. The exact reason for this acidic response is unknown but is demonstrable. It has also been discovered that lead oxide particles with an average particle diameter size of about 5 microns or less also are ineffective as a protective component in the present composition. Although the reason for this is not definitely know, it is believed that such small size lead oxide particles act in concert with the remaining ingredients of the composition as if they are plastic in nature and, as such, do not exert a suitable anticorrosive effect on the composition, nor does such composition as a whole have a suitable lubricating effect.

However, it has also been discovered that when the average diameter size of the particles of lead oxide in the composition is from about 30 to about 45 microns, the advantages desired for the composition are achieved. Thus, the lead oxide particles act to effectively protect the substrate against corrosion over an extended period of time even in normally highly corrosive environments. Moreover, the composition has a suitable lubricating effect on the substrate to prevent galling and wear of the substrate. This protection against corrosion extends to such highly corrosive environments as sea Water and the like. Apparently, although it has not been definitely established, the components of the grease-containing vehicle portion of the composition act to coat the suitably sized particles of the lead oxide in a manner which permits the particles to slip past one another and function in a lubrieating manner While still permitting their anticorrosive effect to occur.

If the lead oxide particles are provided in a larger average diameter size than about 45 microns, the essentially continuous protective layer provided by the oxide particles tends to become disrupted, so that anticorrosion protection begins to decrease. Moreover, it is difficult to assure that lead oxide particles in excess of about 45 microns (average diameter) will remain in uniform suspension in the composition over an indenfinite period of time. Accordingly, about 30-45 micron range for the average diameter of the particles of the lead oxide in the present composition has been found to be the effective range for the composition which provides both suitable lubricating and corrosion protective characteristics for the composition, while causing the composition to exhibit a stable form over an extended period of time of storage and use. It has also been found that the lead oxide particles in the optimal desired characteristics of the composition are provided when the lead oxide particles in the composition have an average diameter of about 32 to about 44 microns, most preferably about 32-35 microns.

The lead oxide particles can be sized in any suitable way, for example, by griding and then screening through a suitable mesh screen, eg through a 325 mesh screen having an average diameter of 40 microns. The lead oxide constituent of the present composition may be any suitable lead oxide or mixture of two or more lead oxides. Preferably however, the lead oxide is red oxide e.g. Pb O and/or litharge. Litharge is PbO. Thus, the lead oxide, if desired, may consist of any suitable mixture of red lead and litharge. Various other forms of lead such 'as Pb O and Pb O can be used, but are less desirable, either from corrosion protection standpoint or because of cost, or both. Accordingly, the most preferable lead oxide for the present purposes is either litharge or red lead or a mixture thereof.

GREASE-CONTAINING VEHICLE The present composition also contains a grease-containing vehicle. The grease-containing vehicle comprises an essentially homogeneous uniform mixture of grease in a major proportion and lubricating oil in a minor proportion. However, it will be understood that in certain instances a different weight ratio of grease to lubricating oil can be used. For most purposes, however, only a relatively small amount of lubricating oil is present in the grease-containing vehicle. Both the lubricating oil and the grease may be any suitable commercially available product.

4 LUBRICATING OIL In calculating the amount of lubricating oil in greasecontaining vehicle, that oil which is initially associated with and is part of the grease itself is not included. Thus, by lubricating oil in minor proportion is meant noncorrosive lubricating oil separately added in minor proportion to a suitable grease in formulating the present greasecontaining vehicle. Such lubricating oils should be present in a concentration in the grease insufiicient to separate from the grease under conditions of normal usage but sufficient to act to lubricate the lead oxide particles in the manner described above. It has been found for such purposes, concentrations of about 1 to about 30 parts of the lubricating oil to 99 to about 70 parts of the grease in the grease-containing vehicle are most suitable. Preferred ratios are about 1 part oil to 4-5 parts by weight of the grease. Preferably, extreme pressure or high pressure lubricating oil is used. These are terms well-known to the oil lubricating art and are used in their usual sense. Extreme pressure and high pressure lubricating oils usually are petroleum grade oils which contain small concentrations, usually about 0.1-0.5 percent by weight of additives which act at high temperature to form high melting point inorganic lubricant films to avoid massive Welding and breakdown of lubricated substrates. Such additives may comprise, for example, sulfur, chlorine, phosphorus or the like compounds in suitable organic form. These compounds may provide low shear strength areas or act as fiuxing agents for contaminated metallic surfaces to prevent welding under pressure. Gear oil which may contain tallow or the like to minimize scuffing and wear during use can also be utilized as the lubricating oil. It will be understood that for the purposes of the present invention any suitable lubricating oil may be used, such as gear oil, high pressure or extreme pressure lubricating oil, or standard lubricating oil of any suitable viscosity, for example 20-30 SAE, with or without additives.

GREASE The grease in the vehicle may be any suitable grease known in the lubricating and protective coating art which is non-corrosive in nature and capable of withstanding elevated temperature and pressure conditions. What is termed heavy duty grease and is well known as such in the art is preferred. Chassis grease or other grease can be used. Such grease may be, for example, a lubricating petroleum oil suitably thickened with a gelling agent such as a fatty acid soap of lithium, calcium, sodium, aluminum or barium or a mixture thereof. The fatty acid may be, for example oleic acid, palmitic acid, stearic acid or other carboxylic acid derived from tallow, hydrogenated fish oil, castor oil or the like. Certain synthetic greases can be used, for example, those diester greases from diester oils such as di-(Z-ethylhexyl)-sebacate. Silicone grease and various radiation-resistant greases can be used. The grease should have a sufiiciently high viscosity so that when utilized in a suitable mixture with the added lubricating oil, it provides both a lubricating effect and an adhesive protective coating effect when disposed on the metallic substrate to be protected. It will be obvious to those who are skilled in the art that a wide range of viscosities for the grease and the resulting grease-containing vehicle can be employed, depending on the particular applications of the composition. Petroleum oils are present in over about 99% of the greases commonly used as protective coatings. The petroleum oil in such greases usually has an SAE rating of about 20-30 with a 100 F. viscosity of about 200-600 SUS. Some lubricating oils also contain amines, phenolics, phosphates, sulfur, selenium and the like inhibitors, usually at 0.1-0.5 weight percent concentration therein. If desired, they can be used as the lubricating oil portion of the grease or the lubricating oil component of the grease-containing vehicle.

It will be understood that both the grease and the added lubricating oil in the grease-containing vehicle must be substantially noncorrosive in character and capable of providing the desired viscosity for the vehicle and also the desired lubricating effect for the substrate and the particles of lead oxide. Neither the grease nor the lubricating oil need contain additives although additives are not excluded from the scope of this invention. It is within the skill of one versed in the art on the basis of this specification to readily provide suitable compositions including the grease and the lubricating oil in proper mixtures.

PREPARATION OF COATING COMPOSITION The grease-containing vehicle is provided by mixing together, to form the essentially homogeneous non-separating mixture, the selected grease together with the added lubricating oil in a proper mixture. The mixing may be, for example, mechanical mixing at low or relatively high speed, depending upon the viscosity of the grease-containing vehicle. As indicated above, such vehicle preferably contains a ratio, by weight of the vehicle, of added lubricating oil to grease of about 1:45. It is also a part of the present invention that the vehicle can contain the added lubricating oil in major proportion and the grease in minor proportion, but this is unusual.

In accordance with the present invention, the lead oxide or oxides are blended together with the grease-containing vehicle to provide a uniform, stable, non-separating mixture. The blending may involve any suitable blending procedure to provide the uniform mixture, as by mechanical stirring or the like. The lead oxide or oxides are present in the coating composition in a concentration of about 40 to about 70 percent, by weight of the coating composition. It has been found that concentrations of less than about 40 percent, by weight of the coating composition, of the lead oxides are ineffective for extended heavy duty anticorrosive and lubricant use. Concentrations in excess of about 70 weight percent of the lead oxides in the composition of the present invention are unnecessary and may be undesirable, particularly when the compositions contain lead oxide concentrations in the 80 Weight percent and above range. Sufficient anticorrosive and lubricating effect is achieved by utilizing the lead oxides of the desired and indicated average diameter size range in a Weight concentration of about 40-70 percent and it is unnecessary to have any greater percentage than about 70 weight percent of the lead oxide particles present in the composition. When the concentration of the lead oxide particles substantially exceeds 70 weight percent not only is the composition substantially more expensive, while not providing an improved result, but difiiculties may be encountered in providing a stable composition which does not have a tendency for the particles to separate over an extended period of time from the remaining constituents in the composition. Concentrations of lead oxide particles well above the said 70 weight percent concentration maximum may also have a tendency to disrupt the continuity of a film of the composition so as to depreciate its lubricating purposes and/or anticorrosion characteristics over an extended period of time. Weight losses of the composition over extended usage may increase. Accordingly, for the purposes of the present invention the concentration of the lead oxide particles in the composition is limited to a range from about 40-70 Weight percent of the composition, with the grease-containing vehicle comprising the remainder of the composition. Preferably, the composition consists essentially of these two components, although the presence of other ingredients, such as thickening agents, inhibitors, etc. is not precluded. Such inhibitors and thickening agents have been previously described.

It has also been found, under certain circumstances, the maximum protective effect of the composition is exhibited when the concentration of the lead oxide particles in the 6 composition approximates 45-55 Weight percent, most preferably about 50 weight percent of the composition. For extreme load conditions the lead particles may comprise as much as 65 Weight percent of the composition.

Certain features of the present invention are further illustrated in the following specific examples.

EXAMPLE I An improved lubricating and anticorrosive coating composition suitable for heavy duty use in marine and other environments is provided by mixing together the following constituents as set forth in Table I below:

TABLE I Ingredients: Percent by Weight Litharge (40 micron average dia.) Heavy duty commercial grease 25 High pressure commercial oil 5 The above-indicated composition of Table I is provided by first mechanically blending together at low speed the heavy duty grease and the high pressure oil and then adding to the resulting mixture to provide the uniform, essentially nonseparating composition of the present invention, the particles of lead oxide while continuing the mechanical blending. Litharge is sized before use by pulverizing it and selecting those particles passing through a standard 325 mesh screen. A parallel composition to that of Table I and having comparable properties is obtained when commercial red lead of the same particle size is substituted forthe litharge, when axle grease is substituted for the heavy duty grease and when SAE 30 lubricating oil is substituted for the high pressure oil.

The composition of Table I, when spread as a inch thick film on panels of cold rolled steel previously acid cleaned and prepared as per federal test standard 141 and exposed, after coating, to immersion in an aqueous solution containing 20 percent by weight of sodium chloride, at a temperature of 150 F. for 24 hours with mechanical stirring demonstrates essentially a low loss of film thickness, and no corrosion of the substrate in contact with the film. When the identical procedure is followed in testing parallel Samples A, B, C and D certain important differences are discernible. Sample A contains only the grease-containing vehicle, i.e. the grease and oil of Table I but no lead oxide. Sample B contains 70 percent by weight of the vehicle (grease and oil) of Table I and 30 percent by weight of the lead oxide, rather than the 70 percent by weight of lead oxide called for in Table 1. Sample C contains 55 percent by weight of the vehicle (grease and lube oil) and 45 percent by weight of the lead oxide, while Sample D contains 45 percent by Weight of the vehicle and 55 percent by weight of the lead oxide. All ingredients are the same ones listed in Table I. When tested for film adhesion under the same conditions specified above for the composition of Table I, over percent of the film is removed when no lead oxide is present (Sample A). About 60 percent of the film is removed when the concentration of the lead oxide in the composition is only about 30 weight percent (Sample B). However, Samples C and D- containing respectively, 45 and 55 weight percent of the lead oxide exhibit an average film loss of only about 50 percent. Accordingly, it is demonstrated by the above test that the adhesion of the composition to the metal under corrosive conditions is substantially increased through the use of high concentrations of the lead oxide in the composition.

EXAMPLE II Parallel test samples of the coating composition of the present invention are provided for testing in the manner set forth in Example I; but containing the following constituents:

In each instance, Samples 1-9 are prepared by blending together the individual constituents, that is, the grease, the oil and the lead oxide to provide a uniform homogeneous mixture. The lead oxide in each instance has an 20 average particle size diameter of about 32-44 microns. Each of Samples 1-9, inclusive, is tested by spreading it as a inch thick film on the surface of a clean cold rolled sheet panel of steel and then immersing the coated panel in an aqueous bath containing 20 percent by weight 25 of sodium chloride, at a temperature of 150 F. The plate is held in the bath for a period of 200 hours with stirring of the bath through the use of a mechanical stirrer. Under the foregoing circumstances, the compositions represented by Samples 1-4 exhibit substantial corrosion 30 of the steel panel with removal of all or a Substantial portion of the film. The panels coated with Samples 5-9 exhibit no corrosion of the steel panel. However, in the case of Sample 9 the final thickness of the film is relatively small (about 20 percent), demonstrating the re- 35 duced adhesivity of the coating containing more than about 70 weight percent of the lead oxide. Some difficulty in the making up of Sample 9 is encountered, particularly in uniformly suspending the litharge and of retaining the suspension over the test period.

EXAMPLE III Parallel samples are provided in the manner described in Example I but utilizing the composition set forth in Table III below: 45

TABLE III Average Percent by weight micron size of lead Com. high oxide Commercial Com. heavy pres. lube r Sample No. particles red lead duty grease oil rosion on panel interface Sample No. with film Thickness of resulting film at end of test (35 10 Extelnsive None.

. Very thin (less than ,r").

None.

. Very thin (less than z).

Less than Me inches. 70 17 ..do Do.

Table IV indicates that even with the same composition as that of the present invention, but with the micron size of the lead oxide particles outside the range specified for the composition, the anticorrosive effect desired for the composition is not obtained. This is the case whether the composition contains 40 percent or 70 percent by weight of the lead oxide. No such corrosion occurs when the average micron diameter size is about the desired range, for example, when it is 50 microns, or when it falls within the desired range, for example 35 micron size, whether 40 percent by weight or 70 percent by weight of the lead oxide is present. However, when the micron size of the lead oxide is above the desired range, for example when it is at 50 microns, the thickness of the film substantially decreases and failure of the film can ultimately occur (Samples 12. and 15). Accordingly, the micron size diameter of the particles of the lead oxide in the composition is important in providing the improved results.

Tests measuring the lubricity as well a the anticorrosive protective nature of the coating compositions indicate the desirability of having the micron size of the particles within the desired and claimed range. In testing the lubricity of the composition, anti-gelling and antiseizure protection is provided by the present coating composition for bearings and other moving parts of heavy duty machinery exposed to salt spray and the like, in contrast to other coating and lubricating compositions, even those containing up to 10 weight percent of lead oxide and/or organic antiwear substances.

As an example of the superior lubricating and anti-cor rosion properties of the present composition, it has been used as the lubricating grease in a Ford Model 4500 tractor equipped with a Model 755 backhoe and a Model 740 loader. The grease is applied by pumping into the grease fittings at the points of stress and strain of the combination unit and use of the composition has resulted in a considerable reduction of failure and wear of the components so lubricated. The composition used is that set forth in Table I above, prepared as described in connection therewith.

Various changes can be made in the present composition, for example, in the grease component, or in the particular lubricating oil, the overall viscosity of the grease and the oil, and in the lead oxide while retaining the advantages of the composition. All such changes in the present composition, its components and in the method of making the composition as are within the scope of the appended claims form a part of the present invention.

What is claimed is:

1. An improved heavy duty coating composition for protection against corrosion and for lubrication of metallic substrates, said composition comprising a substantially uniform mixture of an essentally homogeneous greasecontaining vehicle which comprises grease in major proportion and lubricating oil in minor proportion and from about 40 to about 70 percent, by weight of said composition, of lead oxide in particulate form having an average diameter size of about 30-45 microns.

2. The coating composition of claim 1 wherein said grease-containing vehicle comprises grease in major proportion and lubricating oil in minor proportion, said lubricating oil being present in said grease in a concentration insufiicient to separate readily from said grease but sufiicient to lubricate said particles of lead oxide and wherein said lead oxide comprises at least one of PbO and Pb O 3'. The composition of claim 2 wherein said grease comprises heavy duty grease, and wherein said lubricating oil comprises high pressure lubricating oil.

4. The coating composition of claim 1 wherein said average diameter size is about 32-44 microns and wherein said coating composition consists essentially of said lead oxide particles and said grease-containing vehicle.

5. The coating composition of claim 3 wherein said average diameter size is about 32-44 microns, wherein said lubricating oil is present in said grease-containing vehicle in a weight ratio to said grease of said vehicle of about 1:5.

6. The coating composition of claim 3 wherein said lead oxide consists essentially of at least one of PbO and Pb O 7. The coating composition of claim 3 wherein said lead oxide is at least one of PbO and Pb O and is in a concentration of about 45-55 percent, by weight of said composition, wherein said average diameter size is about 32- 44 microns, wherein said coating composition consists essentially of said lead oxide and said grease-containing vehicle, wherein the grease of said grease-containing vehicle consists essentially of heavy duty grease, wherein said lubricating oil consists essentially of high pressure lubricating oil wherein the weight ratio of grease to lubricating oil in said vehicle is about 5:1, and wherein said coating composition is eflective for lubrication of ferrous metal substrates and for protection against corrosion thereof in marine and other corrosive environments.

References Cited 0 DANIEL E. WYMA-N, Primary Examiner I. VAUGHN, Assistant Examiner U.S. Cl. X.R. 

